Year in review: Big stride for superconductivity

Hydrogen sulfide sets temperature record

UNDER PRESSURE The compartment in the middle of this copper-titanium casing contains two diamonds that crush substances to enormous pressures. Experiments inside this apparatus showed that a hydrogen-sulfur compound is a superconductor at relatively high temperatures.

Mikhail Eremets

After a two-decade hiatus, superconductors are again heating up.

A compound of hydrogen and sulfur, when crushed at more than a million times Earth’s standard atmospheric pressure, appears to whisk electrical current along without resistance at temperatures up to 203 kelvins. That’s not exactly balmy — it’s −70° Celsius — but the current record holder performs its magic at temperatures no higher than 164 kelvins.

A room-temperature superconductor would enable robust energy storage devices, MRI machines that don’t require liquid helium coolant and a new generation of levitating trains. But after more than a century of intense research, physicists still aren’t sure exactly which compounds are capable of reaching that goal. Any new superconductor, even one

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